The term "hermetic" as used herein means an airtight seal, as generally understood in industry and defined by the McGraw Hill Dictionary of Scientific and Technical Terms, 3rd Ed., 1984, McGraw Hill Book Company, New York, N.Y. The military definition of a hermetic seal is more specific and means, in particular, to a barrier through which water may not pass by means of conduction, diffusion, or osmosis. The apparatus and method of the present invention provides a hybrid integrated circuit apparatus in which electrical components are mechanically and electrically coupled, as well as hermetically sealed within a circuit board, by either the generally accepted or military definition of "hermetic" as explaned hereinafter.
Prior to the advent of semiconductor integrated circuits, variety of attempts were made to integrate miniaturized discrete electrical components within a circuit board itself. U.S. Pat. Nos. 3,142,783; 3,192,307; 3,266,125; and 3,290,756 all disclose methods or apparatus in which electrical components are disposed within a circuit board with the electrical interconnections made on the surface of the circuit board.
U.S. Pat. No. 3,142,783, Warren, discloses an electrical circuit system in which electrical components are recessed within apertures in a circuit board. An electrically conductive material, having overlying tabs adjacent each aperture, is bonded to the outer surfaces of the circuit board and serves to retain the electrical components within the apertures and provide electrical connections. Excessive conductive material is then removed to define the proper circuit paths among the components. The components are not hermetically sealed within the circuit board as required by many applications including military applications. Furthermore, a large number of steps are required to produce the apparatus.
U.S. Pat. No. 3,192,307, Lazar, discloses a connector for electrical components on printed circuit boards. In the Lazar patent, a connector element, formed of an insulating material, having an adhesive coating on its underside and a plurality of conductive members connected thereto, is positioned over an electric component disposed within an aperture in the printed circuit board. The conductive members on the connector element provide both mechanical and electrical coupling of the component to the printed circuit board. As with the Warren patent, the Lazar apparatus does not hermetically seal the component within the printed circuit board and furthermore the connector element can be impractical where a large number of components are integrated within a small area.
U.S. Pat. No. 3,266,125, Tobolski, discloses a method for making electrical circuit modules including the steps of soldering a plurality of electrical components between two conductive sheets to form a single unit. The resulting unit is placed in a mold to allow entry of a non-conductive material between the conductive sheets. Selective portions of conductive sheets are then removed to form the required circuit paths. As with the prior art, the components of the resulting board are not hermetically sealed within the circuit board. Furthermore, the method of forming the board and then defining the electrical circuit paths is highly complicated and cumbersome.
U.S. Pat. No. 3,290,756, Dreyer, discloses a method of assembling interconnecting electrical components. In Dreyer, a plurality of electrical components are disposed within holes in a circuit board. Insulating sheets, having connecting patterns of conductive adhesive on their undersurfaces are placed in contact with both sides of the circuit board. The conductive adhesive is then cured to physically bond the sheets to the components and board and to electrically interconnect the components. Although the components of the resulting apparatus are hermetically sealed within the circuit board, the apparatus is impractical for replacement of a defective component due to the unitary sheets covering both surfaces of the apparatus.
None of the above methods or apparatus has gained wide spread acceptance probably due to either the complexity of the manufacturing process or shortcomings of the apparatus design.
Accordingly, it is an object of the present invention to provide a hybrid integrated circuit apparatus in which at least one electrical component is mechanically, electrically and hermetically coupled within the circuit board.
A further object of the present invention is to provide a hybrid integrated circuit apparatus in which a single means is used to mechanically, electrically, and hermetically couple the component within the printed circuit board.
Another object of the present invention is to provide a fast and economical method for manufacturing a hybrid integrated circuit apparatus having at least one electrical component mechanically, electrically and hermetically coupled within the circuit board.
Yet another object of the present invention is to provide a means for mechanically, electrically and hermetically coupling an electrical component within a circuit board which can compensate for the thermal expansion and contraction of the board without affecting the integrity of the hermetic seal or the electrical contact with the board.